EP1050420B1 - Method and control of the temperature of an evaporator in a vehicle air conditioner - Google Patents

Description

The invention relates to a method for controlling the evaporator temperature in a vehicle air conditioning system according to the preamble of the claim 1.

Air conditioning systems in vehicles are generally known. Usually compacted a compressor a gaseous refrigerant and when flowing through the Refrigerant through a condenser, an expansion device and an evaporator the air also flowing through the evaporator is cooled. The air temperature is usually reduced to a temperature of about 1 ° C to 3 ° C. Since these are usually below the dew point of the suctioned for cooling Air is present, water condenses on the evaporator, which becomes air dried. In the following, the cooled one is in most operating states Air warms up again so that it is optimally temperature-controlled in the interior arrives. The cooling regardless of the air conditioning requirement to 1 ° C to 3 ° C therefore usually requires too much cooling capacity.

Therefore, it will a. Object of the following invention, the air conditioning system Always operate only in such a way that the air reaches a precisely required temperature is cooled. It is necessary to set the evaporator temperature and according to the requirements in the vehicle.

DE 196 08 015 C1 describes an air mixing method for an air conditioning system Vehicle known to reduce energy consumption, in which u. a. also the specific one Enthalpy for mixing fresh and recirculated air is taken into account. In particular becomes a mixed air with the smallest specific Enthalpy difference provided. To find the specific enthalpy the temperature and the relative humidity of the air is measured. An evaporator temperature control is not known from DE 196 08 015 C1.

DE 197 28 578 A1 describes a method for controlling the evaporator temperature depending on the dew point known in which the air temperature and the dew point temperature that of the air conditioner for air conditioning an interior of air sucked in from outside and determined from indoor temperature setpoint a counter heating-free evaporator request temperature is determined. In particular, a setpoint is used, which as the smaller value of an evaporator request temperature on the one hand and the Difference from air temperature minus dew point temperature of the supply air on the other hand is chosen.

DE 42 12 680 A1 describes a control device for controlling the output power of a compressor in an automotive air conditioner. In doing so Target cooling temperatures are calculated based on characteristic schemes, and the first target cooling temperature depending on the heat load signals and the second target cooling temperature depending on the outside temperature. A Selection circuit selects the lower of the two target cooling temperatures, where as a result, a reduction in dehumidification performance is prevented.

JP 60176809 describes a vehicle air conditioning system in which an evaporator temperature is selected from two determined temperatures, namely a first temperature to maintain the present room temperature and a dew point temperature, which is the relative humidity at or below holds a predetermined value. Using this approach can save energy A pleasant air conditioning control can be achieved.

The object of the present invention is a method for operating an air conditioning system to develop further in all comfort and safety conditions Is taken into account.

This object is achieved by the features mentioned in claim 1. To avoid of an unnecessary energy consumption will raise the evaporator temperature set a temperature value that reflects both the comfort and safety aspects Takes into account. First, an evaporator temperature value is related determined a certain humidity. The other is an evaporator temperature value determined to ensure sufficient cooling capacity. thereupon the smallest of the aforementioned evaporator temperature values is selected. The evaporator temperature value, which is related to a desired humidity is determined, is dependent on hardware criteria the vehicle windows and comfort criteria. With that becomes one ensures that the driver's view is not impaired. To the others are in a pleasant, not too dry indoor climate for the Respected vehicle occupants. There is a maximum permissible for both cases Air humidity in the vehicle. So the dew point of the air allows the temperature the inner surface of the panes that have to be calculated do not fall below. A maximum permissible serves as the comfort limit Enthalpy of the air in the vehicle interior resulting from humidity and temperature is determined.

The interior humidity is, among other things, a function of the water vapor emission of the occupants, as well as the amount and humidity of the blowing air. The blowing air condition is to be influenced, among other things, by the evaporator temperature. It must be set so that the interior humidity exceeds the permissible limits to comply with the hardware and comfort requirements.

The evaporator temperature value, which is based on a sufficient cooling capacity, is due to the target injection temperature and the undesired heating in the air duct components that follow the evaporator are influenced. Preferably, when determining which to ensure an adequate cooling assigned evaporator temperature the interior temperature, the ambient temperature and / or the solar radiation considered as influencing factors for undesired warming.

A particularly preferred embodiment is characterized in that that to the aforementioned method only when certain operating conditions exist is switched. This is in critical operating conditions ensures that the evaporator temperature is always sufficiently low.

Fig. 1

eine schematische Darstellung einer Klimaanlage in einem Fahrzeug,

Fig. 2

eine schematische Blockskizze des Kältekreislaufs einer erfindungsgemäßen Ausführungsform einer Klimaanlage mit Ansteuerung,

Fig. 3

ein Blockdiagramm, welches die Wirkungskette zur Ermittlung des Innenraumkomforts darstellt,

Fig. 4

ein Blockdiagramm, welches die Wirkungskette zur Ermittlung des Scheibenbeschlags darstellt,

Fig. 5

ein Blockdiagramm, weiches die Wirkungskette zur Einhaltung der Leistungsgrenze darstellt,

Fig. 6

ein Blockdiagramm, welches die Bedingungen für eine erfindungsgemäße Verdampfertemperaturregelung darstellt,

Fig. 7

ein Blockdiagramm, welches die Auswahlkriterien für die Verdampfertemperatur darstellt,

Fig. 8

ein Blockdiagramm, welches die Verdampfertemperatur unter Beachtung des Feuchtekriteriums darstellt

Fig. 9

ein Blockdiagramm, welches die Verdampfertemperatur unter dem Kriterium der Kühlleistung darstellt sowie

Fig. 10

Blockschaltbild, welches einen Aufbau für eine erfindungsgemäße Verdampfertemperaturregelung im Fahrzeug zeigt.

The invention is explained in more detail below with the aid of a special exemplary embodiment - also with regard to further features and advantages - and with reference to the accompanying drawings. The drawings show in

Fig. 1

1 shows a schematic illustration of an air conditioning system in a vehicle,

Fig. 2

1 shows a schematic block diagram of the refrigeration cycle of an embodiment of an air conditioning system with control,

Fig. 3

1 shows a block diagram which shows the chain of effects for determining the interior comfort,

Fig. 4

1 shows a block diagram which shows the chain of effects for determining the window fitting,

Fig. 5

a block diagram representing the chain of effects for compliance with the performance limit,

Fig. 6

2 shows a block diagram which represents the conditions for an evaporator temperature control according to the invention,

Fig. 7

a block diagram showing the selection criteria for the evaporator temperature,

Fig. 8

a block diagram showing the evaporator temperature taking into account the humidity criterion

Fig. 9

a block diagram showing the evaporator temperature under the criterion of cooling capacity and

Fig. 10

Block diagram which shows a structure for an evaporator temperature control according to the invention in the vehicle.

In Fig. 1, a vehicle is shown in a schematic plan view, in which an air conditioning system with compressor 101, evaporator 102, dryer 103 and Capacitor 104 is arranged. According to the invention, by varying the Evaporator temperature is the temperature and humidity of the blowing air changed for the vehicle. Taking into account the climate comfort for the occupants in the vehicle, the air humidity increases with the evaporator temperature to increase. This option is limited by the danger of the window fitting and a possible reaching of a "muggy limit". Adequate cooling capacity must also be ensured.

The following is an embodiment of a method according to the invention described, wherein logic is used in the context of the method will, depending on the parameters present in the vehicle, such as Outside temperature, inside temperature, etc., a choice of evaporator temperature allowed.

In the present exemplary embodiment, a compressor is used, the stroke volume of which can be varied. Such a compressor is shown in a block diagram in FIG. 2 with the reference number 201 and is controlled by a climate control 208. Different cooling capacities can be varied through different volume flows in the refrigeration circuit of the air conditioning system. As a result, the temperature of the evaporator can be adjusted. To adjust the displacement, the compressor has an electrical input that receives a signal from the control device. In the climate control 208, input signals 206 such as an external temperature specification and the evaporator temperature T _{v are received} . The temperature T _v comes from an evaporator 202, through which the coolant is passed to the compressor, the condenser 204 and the expansion valve 205.

The logic for evaporator temperature control is shown below. The following conditions must be observed when regulating. The comfort for the occupant regarding the humidity must be secured his. Window fogging should be avoided. For cooling a sufficient cooling capacity can be made available. To these conditions In the combination, different relationships have to be fulfilled are taken into account, which are explained below:

The comfort rating for the interior is shown with reference to FIG. 3. Starting from the left, the development of the interior humidity X _inside 307 is shown. An essential factor for the interior humidity X _inside is the blowing-in moisture x _nV 306, which depends primarily on the evaporator temperature T _{V_K} 305, because it is responsible for drying the outside air (humidity ϕ ∞, 301, and temperature T∞, 302) (absolute Outside moisture x∞). The function of the evaporator separation efficiency 304 is decisive for the drying of the outside air.

The interior air is also enriched with water by the occupants, which is expressed by an increase in humidity Δx, 310. The Moisture increase Δx, 310, depends on the number of occupants 308 and the humidity per occupant 309. The number of occupants 308 can over a seat occupancy detection system determines the humidity using specified parameters become.

A specific enthalpy (enthalpy of the moist air) for the passenger compartment h _inside , 311 can be determined from the interior humidity X _inside , 307, and the interior temperature T _inside , 312. This specific enthalpy 311 is now compared with a comfort limit h _max , 313, and must always be smaller than this limit value in the present invention. The permissible specific interior thhalpy h _max , 313, basically comes from a comfort assessment carried out with occupants. In addition, three correction factors are provided, namely a stratification setting 314, the solar radiation 316 and the T _target setting 317. If the driver selects a cold stratification setting or sets a low target temperature on an operating part 317, this can not only have the aim of cooling the interior , but possibly also the desire for fresh air. Here it is possible to correct the maximum enthalpy (h _inside ) downwards.

The comparison of the determined specific enthalpy (h _inside ) with the maximum permissible interior enthalpy h _max is shown by box 318.

In order to create a comfortable environment for the vehicle _occupants with regard to the air humidity, the evaporator temperature T _{V_K} plays a decisive role as explained with reference to FIG. 3. In particular, it should be noted that the enthalpy has proven to be an excellent parameter for assessing interior comfort. In this context, reference is made to the publication by Fanger, PO "Air Humidity And Perceived Air Quality, Laboratory of Environment of Energy, Department of Energy Engineering, Technical University Denmark" dated November 19, 1997. Fanger has found that air quality can be determined particularly well depending on the specific enthalpy, ie on various combinations of air temperature and air humidity.

The next point of the required conditions is the avoidance of Window fitting to be taken into account.

This is explained below with reference to FIG. 4. The sizes shown with reference numerals 401, 402, 403, 404, 406, 408, 409, 410, 407 and 415 correspond to the corresponding sizes in FIG. 3. FIG. 4 shows that the development of the interior humidity x _inside , 407 , is identical to that from the comfort analysis. From X _inside , 407 one can deduce the thawing temperature, which together with the pane temperature T _pane , 413, is decisive for a possible pane fitting. The size dx _{inhomogeneous} , 411, which is connected between the interior humidity X _inside and the thawing temperature T _Tau , should take into account possible inhomogeneities in the air mixing. The air does not have the same humidity everywhere. Rather, z. B. the presence of people irregularities in the moisture distribution. In addition to the thawing temperature T _Tau , 412, the _{inside pane} temperature T _pane , 413, which is also responsible for the fitting, is a function of the outside (T∞) and _inside temperature T _inside , 415. The influencing variable “sunshine” 414 is again found here. During the day, when the sun is shining, the pane temperature increases. At night, however, the cold radiation background - sky - can be taken into account. When comparing the disk temperature T _disk with the _thaw temperature T _Tau , care must be taken that the _thaw temperature T _{Tau is} not below the disk temperature T _disk . The evaporator temperature T _{V_B} in FIG. 4 must be selected accordingly. This results in another criterion for an upper evaporator temperature limit.

The next step is to ensure sufficient cooling capacity received.

With current evaporator temperature values of 1 to 3 ° C, there is no problem with a cooling capacity limit that must be observed. However, if the evaporator temperature is set to a less low temperature, the interior may not be cooled sufficiently. A temperature for the air from the ventilation grilles is determined from a stratification position and the values of inside temperature, outside temperature and set target temperature. If the stratification is set to "cold", depending on the calculation of the control unit, in extreme cases only air taken directly from the evaporator can be supplied to the interior. For the evaporator temperature control, this means that the maximum temperature that can be reached is that which is required for compensation at the ventilation level. To take into account the heating of the air in heated ducts, the temperature limit T _V must be adjusted. This is shown in a schematic manner in FIG. 5. The blocks 502 (ambient temperature), 503 (interior temperature) and 504 (solar radiation) determine the temperature of the adjacent components, which in turn affects the heating of the blowing air 506 in the form of a heating ΔT _heating . As a result of this influence, the evaporator temperature T _{V_P is} still heated until it emerges from the ventilation grilles as the blow-out _temperature T _blow-out , 507.

A higher-level determination of the evaporator temperature T _V from all of the above-described evaporator temperatures can be seen in FIG. 7. Essentially, the lowest value from the evaporator temperature _values T _{V_F} and T _{V_P is selected} as the evaporator temperature to be set, T _V , 705, where T _{V_F} , 703 represents the evaporator temperature from the humidity _criterion and T _{V_P} , 704, the evaporator temperature from the performance _criterion . The moisture criterion in turn results from the fitting criterion 701, which was selected on the basis of the fitting limit, and the comfort criterion 702, which was selected on the basis of the maximum enthalpy of air in the interior. In this connection, reference is made to the explanations relating to FIGS. 3 to 5.

The determination of the evaporator temperature with reference to the output can be seen more precisely from FIG. 9. According to reference number 909, the evaporator temperature T _{V_P} represents a function of the blow-out _temperature T _blow-out and the heating of the blow-in air Δ T _heating . According to blocks 901 to 908 in FIG. 9, the solar radiation P _sun , 901, the sunshine dT _{P_Sonne} , 902, the interior temperature T _inside , 905, the outside temperature T _outside , 903, the inside temperature _surcharge dT _{T_innen} , 906, and the outside temperature _surcharge dT _{T_Outer} , 904, are taken into account. This results in the inflation air _heating dT _heating in 907, which together with the blow-out _temperature as ventilation setpoint T _blow-out , 908, leads to the evaporator temperature T _{V_P} .

The evaporator temperature control from the humidity criterion, which is shown in FIG. 7 at 703, can be determined as specified in FIG. 8. _Sun by means of the sunlight P, 801, the solar influence ie _sun, 802, the desired effect of temperature T _set, 803, the target temperature that is _Tset, 804, the stratification value S 805, the stratification effect ie _{stratification,} 806, and the comfort evaluation _comfort h, 807, the permissible specific enthalpy h _inside , 808, can be determined. Together with the _{inside temperature} T _inside , 809, the inside _humidity X _{inside_K} can be determined.

On the other hand, the _inside temperature T _inside , 813, the outside temperature T _outside , 814, and the solar radiation P _sun , 815, the pane temperature T _pane , 816, can be determined. Taking into account the inhomogeneous distribution dx _inh , 818, as well as the dew moisture X _Tau , 817, the maximum permissible interior _moisture x _{inside_B} , 819 (fitting _criterion ) results. The interior _humidity X _inside , 820, is then selected as the lowest value of X _{inside_K} and X _{inside_B} .

The interior humidity x _inside , 820, together with the increase in humidity by the occupants dx _I , 812, which is determined from the number of occupants n _I , 811, gives the blowing-in moisture x _nV , 821. The blowing-in moisture x _nV , 821, results together with the absolute outside humidity X _outside , 825, and the air mass flow dm _air , 827, the evaporator temperature T _{V_F} , 828. The absolute outside _humidity X _outside , 825, can in turn be determined via the relative outside _{humidity rF outside} , 822, and the outside temperature value T _outside , 823. The air mass flow dm _air , 827, can be determined via the vehicle _speed v _fzg , 824, and the blower _voltage U _bl , 826.

Overall, with the evaporator temperature control specified above a climate control system can be implemented that is comfortable for the conditions the occupants regarding the humidity, avoiding window fogging and ensuring sufficient cooling capacity is sufficient.

In the present exemplary embodiment, however, the control according to the invention is not carried out under every environmental or operating condition. From Fig. 6 it can be seen that the control of the evaporator temperature T _{V is} only carried out in the manner described above when six conditions are met. 1. Fresh air mode must be set (602). 2. Furthermore, the air conditioning system is to be operated in automatic mode (604). 3. Moreover, the outside temperature must be in the range from 0 to 25 ° C (606). 4. In addition, it must not rain (608) and 5. The air output should be greater than or equal to a specified automatic blower air output (612). These quantities can be derived from the respective signals and sensors (reference numbers 601, 603, 605, 607, 609, 610 and 611). In the event of deviations from, for example, fresh air or automatic mode, the evaporator temperature control can also be operated with the diagram shown, but with different limit values and safety measures.

A schematic block diagram for a control device for carrying out the inventive method described above is shown in FIG. 10. The signals solar radiation, outside humidity and air mass flow were not taken into account. The vehicle electrical system 1001 already present in the vehicle 100 provides the necessary temperature data T _I (T _inside ), T _A (T _outside ) and T _V (T _{evaporator temperature) to} a computer 1003. Furthermore, further data of the integrated automatic heating and air conditioning system (IHKA data) are communicated to the computer 1003. The computer 1003 is designed here as a rapid prototyping computer and comprises an evaporator temperature logic 1004, a query device for the presence of required conditions 1005 and a controller 1006.According to the data coming in from the vehicle electronics 1001, an evaporator temperature is read out from the evaporator temperature logic and the Regulated controller 1006, which outputs a voltage signal 1007 to an external input of the compressor 2 (see FIG. 2).

Overall, the present invention is simple and inexpensive realize, since only a few new vehicle components are necessary and a corresponding computer extension in the heating and air conditioning control unit, as well as a controllable, externally controllable compressor. Nevertheless, with the method according to the invention a fuel saving by temporary Raising the evaporator temperature. The tension potential According to this assessment, the annual average is around 25% compared to a conventional regulation. On the total fuel consumption of a vehicle, depending on average consumption vehicle savings of the order of 1 - 4 %.

Claims (8)

1. A method for controlling the evaporator temperature in a vehicle air conditioner unit with an evaporator, a compressor, a condenser and an expansion member, in which the evaporator temperature is set in dependency on operating conditions, in which
   a first evaporator temperature value (T_{V_F}) is calculated in dependency on a misting criterion (X_{innen_B}) and a comfort criterion (X_{innen_K}), a second evaporator temperature value (T_{V_P}) is calculated to ensure sufficient cooling performance and
   the smaller of the two evaporator temperature values is selected as the evaporator temperature (T_V) to be set,
   characterised in that
   as comfort criterion the specific enthalpy (h_innen) is used and the first evaporator temperature value (T_{V_F}) is set in such a manner that the specific enthalpy (h_innen) does not exceed a limiting comfort value (h_max.).
2. A method according to Claim 1,
   characterised in that
   the specific enthalpy (h_innen) is derived from the interior space humidity (x_innen) and the interior space temperature T_innen.
3. A method according to one of the Claims 1 or 2,
   characterised in that
   the window temperature (T_Scheibe) serves as the misting criterion and the misting criterion is set such that the dew point temperature (T_Tau) does not fall below the window temperature (T_Scheibe).
4. A method according to Claim 3,
   characterised in that
   the window temperature (T_Scheibe) is established from the ambient temperature (T∞) and the interior space temperature (T_innen).
5. A method according to one of the foregoing Claims,
   characterised in that
   the second evaporator temperature value (T_{V_P}) is selected in dependency on the heating or cooling on the one hand and the quantity of the forced air input.
6. A method according to Claim 5,
   characterised in that
   in the determination of the second evaporator temperature value (T_{V_P}) the ambient temperature, the interior space temperature, the temperature of the contiguous components and/or the incoming solar radiation are taken into account.
7. A method according to one of the foregoing Claims,
   characterised in that
   a switch-over takes place to a constant evaporator temperature or the generation of a suitable artificial value, if the prescribed operating conditions are not present.
8. A method according to Claim 7,
   characterised in that
   the conditions of fresh air operation, automatic operation, operation without rain, the lowest air power and/or a determined outside temperature range apply.

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